#! perl -slw
use strict;

sub _pathsFrom {
    my( $code, $graph, $start, $path, $seen ) = @_;

    return $code->( @$path, $start ) 
        unless exists $graph->{ $start };

    for my $next ( @{ $graph->{ $start } } ) {
        if( exists $seen->{ "$start-$next" } ) {
            return $code->( @$path, $start );
        }
        else {
            _pathsFrom(
                $code, $graph, $next,
                [ @$path, $start ], 
                { %$seen, "$start-$next", undef }
            );
        }
    }
}

sub pathsFrom(&@) { _pathsFrom( @_, [], {} ) }

my %graph = (
    a => [ 'b' ],
    b => [ 'c' ],
    c => [ 'd', 'j' ],
    d => [ 'e', 'g' ],
    g => [ 'h' ],
    h => [ 'c' ],
    j => [ 'k' ],
);

pathsFrom{
    print join '->', @_;
} \%graph, 'a';

__END__
c:\test>904729-2
a->b->c->d->e
a->b->c->d->g->h->c->j->k
a->b->c->j->k